Stain resistant finishes for wool products, such as wool carpets, have been available since 1987. Owing to intensive marketing campaigns in the USA, consumer response was rapid and by 1989 stainblocked carpets accounted for more than 50% of U.S. domestic wool containing carpet sales. The finishes used in stainblocking are mainly condensates of formaldehyde, furfuraldehyde or benzaldehyde, with phenol sulphonic acids, napthol sulphonic acids or dihydroxydiphenyl-sulphae sulphonates.
The stain-resist polymers are believed to form a layer close to the surface of the wool fiber exposing an anionic shield on the outer surface. This serves to repel other anionic species such as the acid dyes used as artificial coloring in food, for example the dyes FD&C40 and amaranth. However, such stain-resist treatments have less effect against non-ionic organic contaminants and hot beverages such as coffee and other non-ionic organic contaminants. Two particularly different common stains are coffee and red wine. These are often said to be the main staining problem in Europe. Clearly, methods and products are needed to address organic contaminants on wool articles.
Heterogeneous photocatalysis have shown promise as a chemical method for oxidizing and thereby removing unwanted organic compounds from fluids, including water, and air. A UV-illuminated catalyst, such as titanium dioxide, absorbs UV light, which produces electrons and holes that migrate to the surface of the catalyst. At the surface, the electrons reduce adsorbed oxygen, while the holes oxidize organic compounds or adsorbed water molecules.
For example, titanium dioxide is a semi-conductor with a band gap of 3.0 ev (rutile) and 3.2 ev (anatase). When a photon having an energy in excess of the band gap is absorbed by the photocatalyst, an electron is promoted from the valence band to the conduction band. The promotion of the electrons produces a “hole”. The hole and the electron may diffuse to the surface of the photocatalyst where each may chemically react. Surface electrons generally reduce adsorbed oxygen, while surface holes generally oxidize organic compounds or absorbed water molecules. When electrons vacancies (holes) react with water reactive OH radicals and protons are formed.
While the use of photocatalysis for the removal of organic pollutants is generally known, a commercially feasible process for the use of such catalysts on wool products has not been developed.
It is an object of the present system to provide improvement, and overcome the disadvantages and problems of the prior art.